Preparation And Study Of Nanofiber Cathode Material Of La(Ba)SrFeCo(Cu)

Solid oxide fuel cells(SOFCs)are one of the most promising energy conversion devices because of their advantages of energy saving,high efficiency,good fuel flexibility and easy large-scale production.And the traditional SOFCS high temperature operation(more than 1000?)resulting in high operating costs,cell components interaction and other problems,affecting the SOFC commercialization process.Therefore,efforts have been made to reduce the operating temperature to the intermediate temperature(500-800?),thus expanding the selection of materials,reducing the cost of operation and installation,etc.The oxygen reduction reaction(ORR)activity of cathode material is the main factor that determines the medium-low temperature of SOFCs.ORR activity depends on the electrode microstructure and the electrode/electrolyte interface or surface.To optimize the preparation method of the cathode materials such as electrostatic spinning method,sol-gel method and glycine nitrate method can improve the microstructure and morphology of material,increase the ORR activity sites,expanding activity area,has unique surface and interface,for the whole of the cathode of charge transport ways to provide continuous,improve the performance of cathode materials.Among them,the electrostatic spinning method is an effective method that can control the preparation of nanofiber materials.In this paper,sol-gel method and electrospinning method are used to prepare Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3-?(BSFC)cathode materials.The coaxial electrospinning method directly prepares the 3D core-shell structure La_0.6Sr_0.4Co_0.2Fe_0.8O_3-?/Pr O_2-?fiber cathode material.The effects of different calcination temperatures on the microscopic morphology,specific surface area,oxygen catalytic activity and electrical properties of BSFC fiber cathode materials were studied.The morphology,specific surface area,oxygen catalytic activity and electrical properties of a 3D core-shell La_0.6Sr_0.4Co_0.2Fe_0.8O_3-?/Pr O_2-?fiber cathode material with high oxygen catalytic activity on its surface were studied.The result shows:(1)The 3D structured BSFC fiber cathode material(BSFC-F800)prepared by low temperature calcination(800?)has a moderate and well-organized porous structure.Compared with the BSFC powder prepared by high temperature calcination,the BSFC fiber cathode material(BSFC-F800)has a larger specific surface area and porosity,and the particles form good contact,forming a continuous electrode network.Provides an uninterrupted channel for charge transport.In addition,X-ray photoelectron spectroscopy(XPS)analysis shows that low-temperature calcination can effectively reduce the surface Sr segregation,and the ORR activity is enhanced.At 700?,the 3D nanofiber cathode material BSFC-F800 has a lower area specific resistance(ASR=0.128?cm²)and a higher peak power density(MPD=0.51 Wcm^-2),and the voltage decay rate in the100-hour long-term stability test is only 0.0342%h^-1.Low-temperature calcination of nanofibers provides a new strategy for obtaining the microstructure design of medium-temperature SOFC with high activity,high stability and high ORR.(2)La_0.6Sr_0.4Co_0.2Fe_0.8O_3-?/Pr O_2-?(LSCF/Pr O_2-?)fiber cathode material with 3D core-shell structure was prepared by coaxial electrospinning combined with calcination at low temperature for the first time.Compared with traditional LSCF fibers,LSCF/Pr O_2-?fibers release more oxygen vacancies due to the adhesion of Pr O_2-?on the fiber surface,which has higher oxygen catalytic activity than that of LSCF.At the same time,Pr O_2-?can fully contact with oxygen,which is more favorable to the ORR of cathode materials.In addition,there is a heterostructure between the surface of LSCF and Pr O_2-?,which further enhances the ORR activity of the cathode material.At the same time,both nanofiber structure and heterostructure can effectively inhibit Sr O segregation,and further improve the stability of LSCF/Pr O_2-?core-shell fiber as SOFC cathode material.At 700?,the core-shell LSCF/Pr O_2-?fibers have lower area specific resistance(ASR=0.076?cm²),which is 38.2%and 65.1%lower than that of LSCF fibers(0.123?cm²)and LSCF powders(0.218?cm²),respectively.Using coaxial electrospinning to modify the surface of the fiber structure is an effective strategy to obtain high ORR activity and high stability cathode materials.